Systems used to control the movement of devices, e.g., actuation systems, are known in the art and are employed for the purpose of causing one or more devices or elements to be activated or moved in a desired manner in response to an actuation signal. An example of an actuation system application includes one where the system is used to control one or more devices of an internal combustion engine, e.g., a gasoline or diesel engine used to power a vehicle. Actuation systems use for such applications can be configured to activate or cause a desired movement of one or more different mechanical devices or elements that influence engine operation, and which movement can depend on particular engine operation conditions. Examples of particular types of mechanical devices or elements that are activated depend on the type of internal combustion engine and its particular application.
In an example where the internal combustion engine includes a turbocharger, an actuation system for such application can be used to control the positioning of elements that are used in conjunction with the turbocharger, such as waste gates, EGR valves, by-pass valves or the like. When the turbocharger used with the internal combustion engine is a variable geometry turbocharger comprising one or more variable geometry elements, e.g., comprising a plurality of movable vanes disposed within the turbocharger turbine and/or compressor housing, the actuation system used with this type of turbocharger can be coupled to an actuator that effects and controls the movement and positioning of such vanes within the turbocharger depending on the engine operating conditions.
Because such activatable mechanical elements are sometimes known to encounter resistance to movement during operation, actuation systems known in the art are configured to not only provide a control signal to effect the desired amount of device movement, but are configured to intentionally introduce what is referred to as a dither frequency to the control system signal. The system dither is provided at a desired frequency that is calculated to overcome any mechanical or magnetic field effects that could otherwise operate to impair the desired movement of the element. The dither frequency used for this purpose will vary from actuation system to actuation system, but is generally configured to offset the unwanted mechanical and/or magnetic field effects known to exist during operation of the actuation system and its elements to help prevent the elements from sticking or binding during desired actuation movement.
Although actuation systems known in the art incorporate the use of dither to help protect against unwanted binding and/or sticking of elements in an actuation system, there are a number of instances where the use of dither, while effective for some amount of time, does not operate to prevent binding and sticking that will eventually occur and that can impair the desired operation of the actuation elements and the performance of the internal combustion engine. Thus, actuation systems are known to fail in the field due to reduced movement/binding of these elements that can be caused by increased friction, the presence of contaminants, corrosion, and the like. The failure of such movable elements to perform as intended, which can eventually result in failure of the device, and which initially results in poor performance and increased emissions, which are also not desirable.
It is, therefore, desired that a system and/or method be developed that is capable of both operating to help address or delay the onset of binding (or otherwise improper operation) of mechanical elements in an actuation system, as well as provide feedback as to the status of the mechanical element and its relative functionality within the actuation system. This is desired for the purpose of enabling one to be able to take preventative action based on the obtained system feedback in making what could be a proactive adjustment, a relatively minor repair or regular maintenance, thereby avoiding what could result in a poor device performance and/or eventual part failure that could cause a more costly repair or nonrepairable replacement.